sgi/install_prerequisites.sh: install openssl in tools/openssl/ssl

Install openssl in tools to avoid overriding the system ssl.
If installed globally, the system ssl gets destroyed as it's unistalled
and installed again by install_openssl3_0 function in
sgi/install_prerequisites.sh, which changes the state of the ssl. This
causes an issue in other application tasks which use ssl.

Signed-off-by: Sushant Tripathi <sushant.tripathi@arm.com>
Change-Id: I474ccb085726593b80c60dbd699f2b77c25c310c